Enhancing liver blood flow after cardiopulmonary bypass: the effects of dopamine and dopexamine

Abstract

Liver blood flow is reduced after cardiopulmonary bypass (CPB) and both dopamine and dopexamine are used to overcome this. This study compares the effects of these agents on liver blood flow. Thirty patients undergoing elective coronary artery bypass graft surgery were randomized into three groups (n = 10 per group). Six hours after surgery baseline liver blood flow was determined by the percentage disappearance rate of indocyanine green measured by dichromatic auricular densitometery. Patients then received infusions of either: (1) placebo (dextrose 5%); (2) dopamine (4 micrograms/kg/min); (3) dopexamine (1 microgram/kg/min increasing to 2 micrograms/kg/min). One hour after infusion, liver blood flow measurements were repeated. In the dopexamine group the infusion was increased and the measurements repeated another hour later. We found that patient-specific variables and operative details were similar for all groups. Postoperative cardiac index and heart rate were increased significantly by dopamine (cardiac index 2.82 +/- 0.46 l/m/m2 vs 3.28 +/- 0.67 l/m/m2: p < 0.001 and heart rate 87.5 +/- 13.2 vs 96 +/- 16: p < 0.05) and dopexamine at 2 micrograms/kg/min (cardiac index 2.71 +/- 0.53 l/m/m2 vs 3.45 +/- 0.67 l/m/m2: p < 0.05 and heart rate 89.0 +/- 18.9 vs 107.4 +/- 13.6: p < 0.001) compared to placebo (cardiac index 2.97 +/- 0.8 l/m/m2 vs 3.18 +/- 0.9 l/m/m2: p > 0.05 and heart rate 77.2 +/- 7.4 vs 77.3 +/- 8: p > 0.05) despite similar atrial and systemic arterial pressures. The disappearance rate of indocyanine green was not altered during infusion of placebo group (9.0 +/- 3.2%/min vs 7.9 +/- 3.0%/min: p > 0.05) or dopexamine at 1 microgram/kg/min (9.7 +/- 3.1%/min vs 11.2 +/- 4.1%/min: p > 0.05). The disappearance rate was increased with dopamine (6.7 +/- 3.7%/min vs 11.8 +/- 3.0%/min: p < 0.05) and dopexamine 2 micrograms/kg/min (9.7 +/- 3.1%/min vs 13.5 +/- 3.2%/min: p < 0.05). This indicates a 76% increase in liver blood flow with dopamine and a 38% increase with dopexamine. We conclude that dopamine 4 micrograms/kg/min and dopexamine 2 micrograms/kg/min increase liver blood flow, although this may, in part, be related to an increase in cardiac output. Dopexamine shows no advantage over dopamine in enhancing liver blood flow after CPB.

Effect of a miniaturized extracorporeal circulation (MECC™System) on liver function

“…14 It should be taken into account that mild impairment of liver function may already be present in cardiac surgical patients as a result of preexisting heart failure. 15 A possible explanation for the reduction in liver blood flow during hypothermic CPB might be a simultaneous loss of perfusion pressure. 14 Therefore, maintenance of a sufficient perfusion pressure during CPB should be of great interest, especially in patients with pre-existing organ impairment, endangered to develop severe postoperative complications.…”

Capillary leak syndrome after cardiopulmonary bypass in elective, uncomplicated coronary artery bypass grafting operations: Does it exist?

“…18 Furthermore, the patients showed a rather high central venous pressure caused by the volume load and positive-pressure ventilation, and an elevation in venous pressure increases the extravasation of macromolecules. 22 Concerning dopamine, low-dose dopamine (4 µg • kg -1 • min -1 ) was demonstrated to enhance splanchnic blood, 23 and an increase in intestinal blood flow by isoproterenol was shown to increase the capillary filtration coefficient as a result of an increase in microvascular filtration area. 24 Accordingly, increased microvascular filtration can be assumed to occur during low-dose dopamine administration, at least in the splanchnic circulation.…”

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“…A further three randomized controlled trials [28,53,54] concluded that dopexamine had no influence on pHi compared with dopamine or placebo. Dopexamine has also been shown to increase jejunal perfusion (as measured by laser Doppler flowmetry) and ICG dye clearance [55]. …”